> Step 2 of course is figure out how to fashion some sort of charging system so my magical godlike pocket super abacus continues to function after ~days
In the good old days of USB 2 I'm sure you can figure out how to get a stable-enough ~5V power supply that would charge the smartphone.
With USB-C you'd need to reinvent IC manufacturing and figure out a needlessly-fragile and overcomplicated protocol before the phone would even accept any power. Yay for progress!
USB-C works without USB-PD. Plain USB-C is simpler than USB-A since it supplies 1.5A or 3A based on resistors. The USB-C to USB-A and microUSB adapters are just resistors to use legacy USB. Legacy USB power is fairly complicated with different standards for 500mA, 1A, and 2.4A power. The reason it looks simple is that cheap chip is in every charger and device.
You can probably provide at least 2.4A 5V on USB-A, just like providing 3A 5V would be fine with USB-C.
USB-C is a superset of USB-A/B, so you can use exactly the same simple protocol: A short of the D+ and D- pins, per USB Battery Charging.
For a USB-C sink, you don't even need any resistors beyond that, let alone USB-PD. For a USB-C source to be able to charge a legacy USB-B sink, all you need is a single 56 kOhm resistor.
To my understanding, there are ways of wiring a USB-C cable such that only four contacts are active, and behave as a USB 2 cable? (although you can only do USB 2 charging over it, so no PD)
In the good old days of USB 2 I'm sure you can figure out how to get a stable-enough ~5V power supply that would charge the smartphone.
With USB-C you'd need to reinvent IC manufacturing and figure out a needlessly-fragile and overcomplicated protocol before the phone would even accept any power. Yay for progress!